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http://www.thewatchbox.com Jaeger-LeCoultre's Duometre family rocked the world of high horology in 2007. The dual-movement, single-case concept upset centuries of assumptions about how a mechanical watch was supposed to keep time. In 2010, JLC rocked the world again with its second take on the Duometre architecture. With two mainspring barrels, two drive trains, two dials, and a single lightning-second heart, the Duomètre à Quantième Lunaire is two watches in one... make that two *extraordinary* watches. And as one of only 300 in 18-K yellow gold, it's exclusive even by the rarefied standard of the Duometre line. Whereas the 2007 Duometre a Chronographe was designed to optimize the performance of a chronograph in tandem with hours, minutes, and seconds, the Duometre QL strives to achieve utmost chronometric efficiency. One mainspring barrel drives the hours, minutes, and seconds; the second barrel drives the moon phase and date. The result can be significant time loss. While a date and moon indication may seem undemanding compared to the constant beat of a chronograph, the reality is that the protracted engagement and sudden "leap" of these complications requires a huge amount of torque. In a conventional watch, the nightly action of moon and date functions dramatically lowers the balance wheel amplitude and devastates the timing precision. But Jaeger-LeCoultre sidesteps that hazard with a combination of raw power and finesse. The power aspect is provided by a second 50-hour mainspring barrel that drives the date/moon changeover while the first 50-hour barrel keeps the time. Finesse comes in the form of a synchronized chronometric choreography that sees both power trains drive their respective functions while receiving an alternating impulse from a single escapement. The escapement beats six times per second (21,600 VpH / 3hz) and drives the foudroyant "lightning second" hand at six o'clock on the main dial. Each jump of the hand represents a small step forward for the watch's time and calendar indications. Absolute precision is ensured via a unique stop seconds mechanism. Jaeger-LeCoultre includes a two-part synchronizer that first stops the foudroyant at "0" (crown position 2) before zeroing and halting the center seconds hand (crown position 3). This exceptional sequence ensures that the watch can be synchronized precisely to a reference time such as an atomic clock. JLC offers an equally compelling artistic effort to complement the virtuoso performance of the engineering department. An ecru-colored dial with guilloche subdials and skeletonized viewing ports creates a warm ambiance. The skeletonized portion of the dial reveals twin power reserve indicators for the independent mainspring barrels, and the combination of the two ports creates the profile of a crescent moon; it's a thoughtful reference to the poetic moon phase. As a 300-unit limited edition from the 2010 launch of the Duomètre à Quantième Lunaire model, this 18-karat yellow gold variant features exclusive content. To this day, it remains the only yellow gold and skeletonized Duomètre à Quantième Lunaire, and the rich burgundy moon phase disc with golden lunar imagery remains a limited edition exclusive. On the case back, Jaeger-LeCoultre takes a page from the A. Lange & Sohne playbook. The Duomètre à Quantième Lunaire caliber 381 movement is rendered in nickel-copper, also known as "German Silver." This delicate alloy is excruciatingly difficult to work and ruinously costly to finish, but the result is a movement that glows with a warm golden aura virtually unknown in the rhodium-plated annals of modern Swiss watchmaking. The Duometre concept was inspired by an 1881 LeCoultre minute-repeating chronometer pocket watch, and JLC's extraordinary dedication to the challenging German Silver methodology is a tribute to the Duometre's 19th century prototype. In every other respect this Duometre is one of the exceptional few Jaeger-LeCoutlre models finished to the manufacture's highest internal standard reserved for flagship pieces; Lange, Patek, and Vacheron do no better. See this Jaeger-LeCoultre Duomètre à Quantième Lunaire in high resolution images on www.thewatchbox.com Video and content by Tim Mosso.